Motors can act as power sources in some operating conditions, during some part of their operating cycle. Therefore, motor driver electronics sinks power from the motor as well as source power to the motor. For example, regenerative braking as used in some electric vehicles uses the drive motors as generators to provide regenerative braking. The amount of braking is proportional to the power drawn from the motor. For maximum efficiency, the power drawn from the motor to provide braking is recycled back to the vehicle battery.
Another example includes cryogenic coolers. For some cryogenic coolers, the motors provide position control braking or temperature control by acting as a power source, absorbing energy from the fluid, and delivering electrical power, during some part of the operating cycle. The motor drive electronics of a cryogenic cooler system therefore not only sources power to the motor, but also sinks power from the motor.
Thus, in cryogenic cooler systems there is bidirectional power flow to and from the motors, and the motor drive electronics provides energy to the motors and receive energy from the motors during some part of the operating cycle. A small converter has been used in cryogenic cooler drive electronics to sink power from a motor and return power back to the source, for a motor that sourced power. However, the use of a small converter for sinking power from a motor is only useful in cryogenic cooler systems in which a motor is sourcing power, as the motor was in this example. In some cryogenic cooler systems, the energy is simply dissipated in a resistor or other load and converted to heat. Accordingly, the energy flow from the motor has not been effectively harnessed. As a result, the electrical energy is not stored or converted to any other type of work and is therefore wasted. To not waste this power sourced by the motor, it would be advantageous to use a bidirectional LVPS that can both provide power to the motor drive electronics and also sink power from the motor drive electronics, and return power to the power source.